[stable:PATCH v5.4.184 12/22] arm64: entry: Make the kpti trampoline's kpti sequence optional

James Morse
2022-03-15T18:29:31Z

commit c47e4d04ba0f1ea17353d85d45f611277507e07a upstream.

Spectre-BHB needs to add sequences to the vectors. Having one global
set of vectors is a problem for big/little systems where the sequence
is costly on cpus that are not vulnerable.

Making the vectors per-cpu in the style of KVM's bh_harden_hyp_vecs
requires the vectors to be generated by macros.

Make the kpti re-mapping of the kernel optional, so the macros can be
used without kpti.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
arch/arm64/kernel/entry.S | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index a2ec7ef24402..bb456f596c43 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1063,9 +1063,10 @@ alternative_else_nop_endif
sub \dst, \dst, PAGE_SIZE
.endm

- .macro tramp_ventry, vector_start, regsize
+ .macro tramp_ventry, vector_start, regsize, kpti
.align 7
1:
+ .if \kpti == 1
.if \regsize == 64
msr tpidrro_el0, x30 // Restored in kernel_ventry
.endif
@@ -1088,9 +1089,14 @@ alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM
prfm plil1strm, [x30, #(1b - \vector_start)]
alternative_else_nop_endif
+
msr vbar_el1, x30
+ isb
+ .else
+ ldr x30, =vectors
+ .endif // \kpti == 1
+
add x30, x30, #(1b - \vector_start + 4)
- isb
ret
.org 1b + 128 // Did we overflow the ventry slot?
.endm
@@ -1108,15 +1114,15 @@ alternative_else_nop_endif
sb
.endm

- .macro generate_tramp_vector
+ .macro generate_tramp_vector, kpti
.Lvector_start\@:
.space 0x400

.rept 4
- tramp_ventry .Lvector_start\@, 64
+ tramp_ventry .Lvector_start\@, 64, \kpti
.endr
.rept 4
- tramp_ventry .Lvector_start\@, 32
+ tramp_ventry .Lvector_start\@, 32, \kpti
.endr
.endm

@@ -1127,7 +1133,7 @@ alternative_else_nop_endif
.pushsection ".entry.tramp.text", "ax"
.align 11
ENTRY(tramp_vectors)
- generate_tramp_vector
+ generate_tramp_vector kpti=1
END(tramp_vectors)

ENTRY(tramp_exit_native)